1. Field of the Invention
The present invention relates to a multi-point temperature sensing method for integrated circuit chips and a system of the same, especially to a multi-point temperature sensing method for integrated circuit chips and a system of the same in which a master temperature sensor with a large area and a certain precision is used to correct other slave temperature sensors having a smaller area and a lower precision so as to reduce the area the temperature sensors required in integrated circuit chips dramatically and further improve stability of a temperature control system in integrated circuit chips.
2. Description of Related Art
Along with fast development of integrated-circuit technology, more and more transistors are placed on a single chip. According to Moore's law, the number of transistors on integrated circuits doubles every 18 months. With the advancement of manufacturing processes, the size of semiconductor devices moves from deep submicron- to nano-meter scale. An increasing number of logic gates are packed on a single chip. That means more and more functions are integrated on the single chip. Trends in the Very Large Scale Integration (VLSI) technology include more transistors, faster clock rate, lower supply voltage, more circuit layers, and more I/O pins. These trends enable microprocessors, memories, digital signal processors (DSP) and various interfaces included in complicated multi-chip systems to be integrated into a single chip and a System-on-a-Chip (SoC) is formed. However, the complicated functions and the increasing chip density result in excessive power consumption and associated thermal problems. In order to make the SoC operate properly and avoid thermally induced errors or even damages in the SoC, there is a need to provide a method for monitoring the temperature of the SoC and a system of the same.
Generally, an embedded temperature sensor used in SoC is single-point detection. Refer to Taiwanese Pat. Pub. No. I368839 “system for control of chip temperature and method of the same”, the system uses an oscillation ring to detect operating temperature of the chip. Not only the temperature of the chip is detected, the temperature of the chip is also modulated dynamically. The system for control of chip temperature includes at least one temperature sensing unit and a dynamic voltage regulator controller. The temperature sensing unit is built in the chip and is composed of an oscillation ring, a counter and decoder. The oscillation ring has an oscillation frequency that is inversely proportional to the temperature of the chip. The counter is electrically connected to the oscillation ring for recording the oscillation frequency and calculating a value according to the oscillation frequency. The decoder is electrically connected to the counter for determining voltage provided to the chip according to the calculated value. The dynamic voltage regulator controller is electrically connected to the temperature sensing unit for dynamically adjusting the voltage provided to the chip according to determination of the decoder. Thereby the system is easy to be integrated into the design of the chip so as to achieve temperature detection and dynamic modulation. Moreover, the temperature of the chip is monitored in a real time manner so as to regulate the voltage and the clock rate accordingly. Thus the reliability and yield rate of the chip are improved significantly and the optimal operation performance of the chip is ensured. However, the SoC generally includes a plurality of circuits with different functions. Each circuit has different power and temperature corresponding to the function. In order to monitor the temperature of each block of the circuit effectively and prevent circuit malfunction caused by the temperature, there is a need to have a multi-point temperature sensing mechanism in the circuit.
Basically, a temperature sensor with certain precision has a circuit for generating a signal that changes with temperature and having high linearity. Then the signal is converted into digital code to be processed by a digital circuit at the rear end. However, the circuit is usually quite complicated and having a larger area for generating the signal that changes with temperature and having high linearity. This is a great burden for a system that requires several temperature sensors. Refer to FIG. 11, a schematic drawing showing a conventional multi-point temperature sensing system used in integrated circuit (IC) chips. An integrated circuit chip 4 includes a plurality of blocks 41 that execute specific functions respectively. In the block 41, there are many hot spots that need to be monitored by temperature sensors 5. The temperature sensor 5 with certain precision needs a large area. This is due to that most of the temperature sensor 5 uses conventional proportional to absolute temperature (PTAT) circuit to generate PTAT current. Then the current is delivered to resistors in series and temperature voltage with positive temperature coefficient (PTC) is obtained from a plurality of end points of the resistors in series. Next the temperature sensor 5 catches the corresponding temperature voltage and compares the temperature voltage with reference voltage by means of multiplexer and comparator so as to detect ambient temperature. However, the resistors in series occupy a larger area on the chip to have more precise resistance value if users want to get the temperature voltage generated while the current flowing through the resistors in series. These resistors in series are also affected by offset in semiconductor processing. Moreover, during the design of the resistors in series, a pull-up resistor electrically connected to ground potential needs a larger resistance value than other resistors in series so as to pull up the temperature voltage greatly. Thus the temperature voltage and the reference voltage can be compared. The circuit area of the temperature sensor 5 is further increased. Generally, one temperature sensor 5 placed in the block 41 may occupy up to one third (⅓) area thereof. Thus it's unable to arrange many temperature sensors 5 in one block 41. And the stability as well as reliability of the whole temperature control system of the integrated circuit chip is reduced and the damage probability caused by high temperature is increased. There is a need to provide a novel multi-point temperature sensing system that overcomes the shortcomings of the prior art mentioned above.